1. Field of the Invention
This invention relates, generally, to adapter devices having utility in interconnecting marine engines and stern drives.
2. Description of the Prior Art
Only one U.S. company makes diesel engines exclusively for the marine market. Other U.S. companies make diesel engines that are supplied to the marine market, but such engines are primarily truck engines that have been modified for marine applications. The horsepower to weight ratios, i.e., the horsepower to cubic inch displacement ratios of the modified truck engines are not as optimal as are the engines designed exclusively for marine applications. Moreover, the exclusively-for-marine use engines, unlike the modified truck engines, are sleeved engines and possess a reliability and durability unmatched by the modified truck engines. They are fuel injected and operate substantially smoke-free, unlike the marine engines manufactured by the truck engine manufacturers.
The stern drives driven by the engines, whether truck or true marine engines, work best when coupled to high horsepower, high revolutions per minute engines. If an engine produces high horespower at a relatively low rpm, its torque may exceed the structural capabilities of the stern drive to which it is coupled. Accordingly, stern drive manufacturers provide maximum torque specifications, and connection of a stern drive to an engine that produces torque in excess of said specifications will void the warranty on the stern drive. Such warranty-voiding coupling may also result in destruction of the stern drive. Numerous racing competitors have attempted to win races by connecting stern drives to high horsepower, high torque engines that exceed the limitations of the stern drive; the result is usually a destroyed stern drive.
The ideal engine would be light in weight and would produce high horsepower at low torque, i.e., at high engine rpms. A typical marine-modifed truck engine produces three hundred horsepower at twenty eight hundred rpms; this horsepower to rpm ratio is unacceptable for many stern drives because of the excessive torque produced. However, the engines produced solely for the marine market produce even more horsepower at higher engine rpms, i.e., at lower torque.
It would therefore seem logical that in racing competition, the purely marine engines should always prevail over the modified truck engines, but such is not the case. The stern drives that are coupled to the marine-only engines cannot take full advantage of the high horsepower, low torque engines to which they are connected due to their own structural limitations. Similarly, the stern drives coupled to the modified truck engines can handle the high torque supplied to them, but the rpms are insufficient to guarantee success in racing conditions. Thus, the conventional wisdom in the racing industry is that each competitor will have to find the right combination of horsepower, torque, and engine rpms on the engine side of the drive package, and torque limitations on the stern drive side of the package.
At the time the present invention was made, it was not obvious to those of ordinary skill in this art how the best marine-only engines could be used to drive the best stern drives. More particularly, the best marine engines could not even be coupled to the best stern drives due to structural incompatibility therewith.